BIOCHEMICAL AND MOLECULAR ANALYSIS OF PIGEO N PEA IN RELATION TO WILT RESISTANCE
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Date
2003
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MPKV, UNIVERSITY LIBRARY RAHURI
Abstract
The objectives of this investigation were to identify
biochemical constituents associated with wilt resistance and to study the
genomic differences in promising resistant and susceptible cultivars of
pigeonpea. Five wilt resistant and five wilt susceptible cultivars were grown
in a separate pot culture replicated experiments with wilt pathogen free and
wilt - sick soils.
The roots and leaves of 45 - day old plants were analyzed for
various biochemical constituents like cellulose, hemicellulose, lignin, silica,
reducing and total sugars, soluble proteins, free amino acids, total phenolics,
chlorogenic acid and activities of PO, PPO and PAL with standard methods.
The genomic DNA was extracted and isolated from 10 - day old seedlings
of all the cultivars and subjected to RAPD analysis using various kinds of
primers.
The root tissues of resistant group of cultivars were found to
contain significantly higher levels of hemicellulose, lignin, total phenolics
and activities of PO, PPO and PAL under healthy conditions. Similarly, the
leaf tissues of resistant cultivars also contained significantly higher levels of
hemicellulose, total phenolics, chlorogenic acid and activities of PPO and
PAL. However, both roots and leaves of resistant group of cultivars
contained significantly lower values for free amino acids and sugars as
compared to the susceptible types.
When the values on various biochemical parameters of resistant
group of cultivars were compared between healthy and infected plants, the
contents of hemicellulose, lignin, reducing sugars, total sugars and total
phenolics were found to decrease slightly upon infection indicating that
these parameters were constitutionally present in higher amounts in resistant
types. The other parameters viz., chlorogenic acid and activities of PO, PPO
and PAL were found to increase markedly upon infection in resistant
cultivars, indicating that these are inducible parameters.
Several compounds were found to be associated constitutionally
or as induced synthesis, with resistance to wilt. However, none of the
constituents was found remarkably higher in resistant types. Thus, these
parameters might offer a collectiv e resistance agains t wilt infection. A lowe r
level of free amino acids an d sugars in plant tissues mak e it les s favourable
for infection.
Molecular analysis of the resistant an d susceptible pigeonpea
cultivars recorde d a total of 228 DNA fragment s by PC R amplifications
using different primers. Most of the primer s generated 8-1 5 bands in a single
cultivar. Out of 174 amplified fragments generated, 76 wer e obtaine d with
Operon primer s and 98 with UBC primers. The polymorphism range d from
8.51 to 22.58 %. Wilt resistant or susceptible cultivar s could be clearly
discriminated using a wel l selected uniqu e prime r or wit h 5-10 randomly
chosen primers . In DNA fingerprinting , all the cultivar s could be easily
distinguished by random primers except PT-1037. The similarity inde x
values ranged from 0.24 to 0.55 indicatin g a narrow genetic base. The
dendogram based on similarity index values showed three different clusters
of cultivars. Thes e markers could be utilized i n breeding for disease
resistance, gene mapping , an d assessment of the purit y and stability of th e
genotypes entering into the breedin g programmes
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